Abstract

Synthetic pyrethroids such as cypermethrin and deltamethrin have been widely used in Chile to treat sea lice on salmon since 2007. The environmental risks of aquaculture practices are evaluated through the use of several tools such as fugacity-based models for predicting environmental dynamics and the fate of pyrethroids after their release into the marine environment and the determination of pyrethroid occurrence in environmental samples (i.e., water and sediment). For seawater, passive sampling devices (PSDs) are proposed as a good alternative for field monitoring. Finally, by means of ecotoxicological bioassays, the effects of pyrethroids on native biota were assessed. The results show that the application of pyrethroids may trigger some unintended risks to nontarget organisms, particularly copepods, since modeled and observed concentrations in water (dissolved phase) are in the range of fractions of ng/L, but higher cypermethrin and deltamethrin concentrations in sediment in the range of 1,323 and 1,020 ng/g, respectively, have been observed. These measured concentrations were in the range of concentrations toxic to native invertebrate species in Chile. We conclude that a stricter process should be followed when pyrethroids, particularly cypermethrin, are recommended for use in combating sea lice in the Chilean salmon farming industry. Risk assessment procedures and the establishment of stricter regulations on matters such as the maximum allowable concentrations around the cages when these pesticides are applied and recommended.